Audiolingual Method

Kinds of Sentences According to Structure
A sentence may consist of one clause (independent clause) or more clauses (independent and dependent clauses). An independent clause is also called main clause. A dependent clause is also called subordinate clause.

On the basis of numbers of clause and types of clauses present in a sentence, sentences are divided in to four kinds.
Simple Sentence A simple sentence consists of only one independent clause containing a subject and a verb and it expresses complete thought. There is no dependent clause.
“An independent clause (also called main clause) is called a simple sentence.”

Examples. He laughed. She ate an apple. They are sleeping. I bought a book.
Compound Sentence
A compound sentence consists of at least two independent clauses joined by coordinating conjunctions. There is no dependent clause in compound sentence. The coordinating conjunctions use to join independent clauses are “for, and, nor, but, or, yet, so”. Independent clauses can also be joined by a semicolon (;). A comma may or may not be used before the conjunction in compound sentence.

Examples I like an apple but my brother likes a mango. I helped him and he became happy. He failed two times yet he is not disappointed. I asked him a question; he replied correctly.
Complex Sentence
A complex sentence consists of one independent clause and at least one dependent clause joined by subordinating conjunction (because, although, since, when, unless etc) or relative pronoun (that, who, which etc).

Examples I met the boy who had helped me. She is wearing a shirt which looks nice. You can’t pass the test unless you study for it.
If a complex sentence begins with an independent clause, a comma is not used between clauses in a complex sentence. If a complex sentence begins with dependent clause then a comma is use after dependent clause in a complex sentence. See the following example.

He is playing well although he is ill. Although he is ill, he is playing well.
Complex - Compound Sentence
A complex-compound sentence consists of at least two independents and one or more dependent clauses. It is also sometimes called compound-complex Sentence.

Examples 1. He went to college and I went to a market where I bought a book. 2. I like Mathematics but my bother likes Biology because he wants to be a doctor.
In the first sentence of above sentence, there are two independent clauses “he went to college” and “I went to a market”, and one dependent clause “where I bought a book”.
A sentence is a unit of syntactic structure that contains at least one finite clause. It may have more than one clause; if it does, the additional clauses may be finite or nonfinite. There are two main ways of categorizing sentences: by their internal clause structure, and by their functional/grammatical type. We will look at each in turn.
Classifying sentences by internal structure
This means classifying sentences into types based on how many clauses the sentence contains, as well as what relationships the clauses bear to each other, if there is more than one. There are three categories:

Simple sentence: a sentence consisting of only one clause. It will be finite, since the definition of 'sentence' requires a finite clause. Examples: A. The tree | fell. | NP | VP | subject | predicate; past marked verb (present would be falls) | | | B. That big luxury car in the parking lot | belongs to the president of the university. | NP | VP | subject | predicate; present marked verb belongs |

Complex sentence: A sentence containing more than one clause. At least one clause must be finite. The shape of a complex sentence is that of one clause inside another: one of the clauses is the main clause; the other is the dependent or subordinate clause. A subordinate clause acts like a phrase: it acts as a building block for a larger sentence. Subordinate clauses play a grammatical role in the overall sentence just like phrases do: subject, direct object, adverbial, etc.

I | understand. | NP | VP | subject | predicate=one finite clause (a simple sentence) | | | I | understand something. | NP | V NP | subject | predicate (containing a verb + direct object NP something)= one finite clause (a simple sentence) | | | I | understand that my remark was hurtful to you. | NP | V clause | subject | predicate (containing the verb 'understand' and a clause, 'that my remark was hurtful to you') | The predicate in this last sentence contains another clause: | that | my remark was hurtful to you | conjunction | NP VP | clause-embedder | subject predicate |
This is a finite clause on its own: the verb was is in its past form. But the clause plays a role in the overall sentence by being the direct object of the verb understand: remember that a direct object is a person or thing that the action of the verb is directed towards. In this sentence, the understanding of the subject 'I' is directed towards the concept 'my remark was hurtful to you'; this clause names the thing understood.
Since the clause that my remark was hurtful to you is a building block for the overall sentence I understand that my remark was hurtful to you , it is subordinate to the overall sentence.
Subordinate clauses can play all the same roles as phrases: subject, adverbial, and so on. More examples:
a. That she was tired was obvious. Clause VP subject predicate ('was obvious' is a comment about 'that she was tired')
b. I like you because you are a friendly person. clause clause main clause adverbial modifier of main clause: tells why I like you
The subordinate clause in a complex sentence does not have to be finite. A nonfinite clause may also play the role of a phrase (that is to say, a constituent) in a particular sentence. Consider:
I saw Mary eating strawberries.
NP VP (verb + nonfinite clause) subject predicate (Mary eating strawberriesis the direct object of 'saw')
We heard the tree fall.
NP VP (verb + nonfinite clause) subject predicate (the tree fall is the direct object of 'heard')
John having called the waiter, we placed our orders. nonfinite clause finite clause adverbial (tells why or when main clause we placed our orders)

Compound sentence: A compound sentence contains more than one sentence (therefore, more than one finite clause). The component sentences may be simple or complex. The sentences that join to form a compound are independent of one another; that is to say, one is NOT a building block inside the other. They both contribute equally to the compound sentence.
We stayed until the end of the party, but Pete left early.
Compound sentence, consisting of:
We stayed until the end of the party, but Pete left early. finite clause #1; simple sentence + conjunction + finite clause #2; simple sentence (clause joiner)
Pete left because the party was real wild, and we stayed for the same reason!
Compound sentence, consisting of:
Pete left because the party was real wild and we stayed for the same reason
Sentence #1: complex (2 clauses) + conjunction + sentence #2: simple sentence

Classifying sentences by functional/structural type
Another way of classifying sentences is according to their function in communication. Does the sentence make a statement (assert a fact)? Does it ask for information? Does it ask for confirmation of something the speaker thinks is true, but is not sure about? Does it correct an incorrect assumption by a listener? Sentences come in different forms (different grammatical structures) to serve these different functions.
The plainest or most basic type of sentence is the kind that makes a statement, the declarative type (it 'declares' something that the speaker knows to be true). For example:
(1) Jose washed his car today.
Now, imagine various situations in which a speaker and listener are talking about this event of car-washing, but in ways that call for something other than a statement of fact. For instance ...
The speaker wants to know whether Jose washed his car today or not. The listener has that information. The speaker will then form a question of a particular type in order to get that information: a yes-no question.
(2) Did Jose wash his car today?(Yes-no question)
Notice that this sentence differs from (1) in two ways: The word did appears before the subject Jose, and the verb wash is not marked for past: did carries the past tense.
A form of the verb do will appear in yes-no questions that do not already have a 'helping' verb (auxiliary) verb. If there is an auxiliary verb, or if the verb is be, it will appear in front of the subject of the sentence:
(3) Jose has washed his car already. (Has is an auxiliary verb; washed is the main verb.)
(4) Has Jose washed his car already?
(5) Jose will wash his car this weekend. (Will is an auxiliary verb used to indicate future tense.)
(6) Will Jose wash his car this weekend?
(7) Nguyen is the president of the new club. (Is is the only verb; no auxiliary)
(8) Is Nguyen the president of the new club?
Notice that here, the only difference between the statement and the question is that the auxiliary verb was appears as the first thing in the sentence.
Yes-no question form: Aux. verb / is / do + subject NP + main verb + rest of sentence
Let us now imagine some other possible scenarios.
-- The speaker knows most of the car-washing situation, but there is some information lacking. For example, the speaker knows a car got washed, but doesn't know who did the washing. In this case, the speaker will utter an information question, also known as a wh-question (because such questions always contain words like what, when, where, why, who, how, most of which begin with 'wh' in the spelling).